Method and apparatus for measuring distances, and method for determining positions
The present disclosure provides a ranging method by using a first signal transmitted by a first device, and a second signal generated and transmitted by a target device in response to the first signal. The ranging method calculates the distance between the target device and a second device being in communication with the first and target devices, by using: a first time interval from a point in time of first device's transmitting the first signal to a point of receiving first part of the second signal; a second time interval from a point of the second device's receiving the first signal to a point receiving the first part of the second signal; and a delay time interval from a point of the target device's receiving the first signal to a start time of the second signal and a duration of the first part of the second signal.
1. A ranging method by using a first signal transmitted by a first device and a second signal generated and transmitted by a target device in response to the first signal, the method characterized in calculating a distance between the target device and a second device being in communication with the first device and the target device, by using:
a first time interval measured from a time point of the first device's completing transmission of the first signal to a time point of the first device's completing reception of a first part of the second signal, and a third time interval measured from a time point of the first device's completing reception of the first part of the second signal to a time point of the first device's completing reception of a second part of the second signal;
a second time interval measured from a time point of the second device's completing reception of the first signal to a time point of the second device's completing reception of the first part of the second signal, and a fourth time interval measured from a time point of the second device's completing reception of the first part of the second signal to a time point of the second device's completing reception of the second part of the second signal;
a given delay time interval from a time point of the target device's completing reception of the first signal to a start time of the second signal and a given duration of each of the first and the second parts of the second signal; and
a given distance between the first device and the second device.
2. The ranging method of claim 1 , wherein a distance d0 between the first device and the target device is calculated by the following equation, based on the first time interval of counts N01, measured by the first device, of a unit time generated by dividing the first device's clock period by an interpolation division integer and the third time interval of counts N02, measured by the first device, of the unit time:
d 0= D CLK *( N 01− Kr*N 02)/2
Kr =( M gap+ M 1)/ M 2, D CLK =c *( T CLK /M INT ),
where c denotes a transmission speed of a signal in a medium, T CLK denotes a nominal clock period, M INT denotes the given interpolation division integer greater than or equal to 1, Mgap denotes given counts of T CLK /M INT which are used for generating the delay time interval, M1 denotes given counts of T CLK /M INT which are used for generation of the first part of the second signal, and M2 denotes given counts of T CLK /M INT which are used for generation of the second part of the second signal.
3. The ranging method of claim 2 , wherein a distance d1 between the second device and the target device is calculated by the following equation, based on the second time interval of counts N11, measured by the second device, of a unit time generated by dividing the second device's clock period by the interpolation division integer, the fourth time interval of counts N12, measured by the second device, of the unit time, the given delay time interval, the given duration of the first part of the second signal, the given distance between the first device and the A second device, and the calculated distance d0:
d 1= D CLK *( N 11− Kr*N 12)+ D 01− d 0,
where D01 denotes the given distance between the first device and the second device.
4. A ranging apparatus using a first signal transmitted by a first device and a second signal generated and transmitted by a target device in response to the first signal, the ranging apparatus calculating a distance between the target device and a second device being in communication with the first device and the target device, by using:
a first time interval measured from a time point of the first device's completing transmission of the first signal to a time point of the first device's completing reception of a first part of the second signal, and a third time interval measured from a time point of the first device's completing reception of the first part of the second signal to a time point of the first device's completing reception of a second part of the second signal;
a second time interval measured from a time point of the second device's completing reception of the first signal to a time point of the second device's completing reception of the first part of the second signal, and a fourth time interval measured from a time point of the second device's completing reception of the first part of the second signal to a time point of the second device's completing reception of the second part of the second signal;
a given delay time interval from a time point of the target device's completing reception of the first signal to a start time point of the second signal and a given duration of each of the first and the second parts of the second signal; and
a given distance between the first device and the second device.
5. A method for determining a position of a target device by a positioning system including the target device, a master device and one or more slave devices, the method comprising:
generating and transmitting a first signal by the master device;
generating and transmitting, by the target device, a second signal in response to the first signal after elapse of a given delay time interval from completion of reception of the first signal;
measuring a first time interval from a time point of the master device's completing the transmission of the first signal to a time point of the master device's completing reception of a first part of the second signal, and a third time interval from a time point of the master device's completing reception of the first part of the second signal to a time point of the master device's completing reception of a second part of the second signal;
measuring a second time interval from a time point of each slave device's completing reception of the first signal to a time point of said each slave device's completing reception of the first part of the second signal, and a fourth time interval measured from a time point of said each slave device's completing reception of the first part of the second signal to a time point of said each slave device's completing reception of the second part of the second signal;
calculating a distance between said each slave device and the target device based on the measured first time interval, the measured third time interval, the measured second time interval, the measured fourth time interval, the given delay time interval, a given duration of each of the first and the second parts of the second signal, and a given distance between the master device and said each slave device; and
determining the position of the target device by using the distance between said each slave device and the target device.
6. The positioning method of claim 5 , further comprising:
calculating a distance d0 between the master device and the target device, based on the first time interval of counts N01 of a unit time generated by dividing the master device's clock period by an interpolation division integer and the third time interval of counts N02 of the unit time;
calculating a distance di between said each slave device and the target device, based on the second time interval of counts Ni1 (index i=1, . . . , N SLAVE , N SLAVE is the integer number of total slave devices) of a unit time generated by dividing the slave device's clock period by an interpolation division integer and the fourth time interval of counts Ni2 of the unit time; and
determining a position of the target device by using the distance d0, the distance di, and position information of the master device and the slave devices,
wherein the distances d0 and di are calculated by equation
d 0= D CLK *( N 01− Kr*N 02)2)/2
di=D CLK K *( Ni 1− Kr*Ni 2)+ D 0 i−d 0
Kr =( M gap+ M 1)/ M 2, D CLK =C *( T CLK /M INT ),
where c denotes a transmission speed of a signal in a medium, T CLK denotes a nominal clock period, M INT denotes the given interpolation division integer greater than or equal to 1, Mgap denotes given counts of T CLK /M INT which are used for generating the delay time interval, M1 denotes given counts of T CLK /M INT which are used for generation of the first part of the second signal, M2 denotes given counts of T CLK /M INT which are used for generation of the second part of the second signal, and D0i denotes the given distance between the master device and said each slave device.
7. A ranging method using a first signal transmitted by a first device and a second signal transmitted by a second device in response to reception of the first signal, the method calculating a distance between the first device and the second device by using:
a first time interval measured from a time point of the first device's completing transmission of the first signal to a time point of the first device's completing reception of a first part of the second signal, and a second time interval measured from a time point of the first device's completing reception of the first part of the second signal to a time point of the first device's completing reception of a second part of the second signal;
a given delay time interval from a time point of the second device's completing reception of the first signal to a start time point of the second signal; and
a given duration of each of the first and the second parts of the second signal,
wherein a distance d0 between the first device and the second device is calculated, based on the first time interval of counts N01, measured by the first device, of a unit time generated by dividing a first device clock period by an interpolation division integer and the second time interval of counts N02, measured by the first device, of the unit time,
wherein the interpolation division integer is equal to or larger than 1.
8. The ranging method of claim 7 , wherein the distance d0 is calculated by equation
d 0= D CLK *( N 01− Kr*N 2)/2
Kr =( M gap+ M 1)/ M 2, D CLK =c *( T CLK /M INT ),
where c denotes a transmission speed of a signal in a medium, T CLK denotes a nominal clock period, M INT denotes the given interpolation division integer greater than or equal to 1, Mgap denotes given counts of T CLK /M INT which are used for generating the delay time interval, M1 denotes given counts of T CLK /M INT which are used for generation of the first part of the second signal, and M2 denotes given counts of T CLK /M INT which are used for generation of the second part of the second signal.
9. The ranging method of claim 7 , wherein a T CLK /M INT is smaller than or equal to time resolution required for a positioning.